Temperature control system for a gas heated clothes drying machine



Nov. 15, 1966 J. c. WORST 3,285,539

TEMPERATURE CONTROL SYSTEM FOR A GAS HEATED CLOTHES DRYING MACHINE Filed May 6, 1964 5 Sheets-Sheet 1 I so i i i J 2| .-J 49 38 so L443 a 1: 5\' fin J) .12. 4f 22 z car-37 4-2" w \1 J I Q56 N 5 {Z I T a GI e0 2 55 5 1 J W 1 r -5 1 gr I T -58 0 ZS 271g INVENTOR- TOSEPH C- WORST H \s ATTORNEY Nov. 15, 1966 c WQRST 3,285,589

.1. TEMPERATURE CONTROL SYSTEM FOR A GAS HEATED CLOTHES DRYING MACHINE Filed May 6, 1964 5 Sheets-Sheet 2 INVENTOR. JOSEPH c. WQRST H \s ATTORNEX Nov. 15, 1966 J. c. WORST 3,285,589

TEMPERATURE CONTROL SYSTEM FOR A GAS HEATED CLOTHES DRYING MACHINE Filed May 6, 1964 3 Sheets-Sheet :5

INVENTOR. TOSEPH c. WORST M WM Hus ATTORNEY United States Patent Ofitice 3,285,589 Patented Nov. 15, 1966 3,285,589 TEMPERATURE CONTROL SYSTEM FOR A GAS HEATED CLOTHES DRYING MACHINE Joseph C. Worst, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed May 6, 1964, Ser. No. 365,385 7 Claims. (Cl. 263-) This invention relates to gas heater control systems and more particularly to automatic temperature-sensitive control systems for clothes drying machines.

Domestic clothes drying machines accomplish their drying function by tumbling clothes in a rotating drum while passing a stream of heated air through the drum. At the beginning of the drying cycle, when the clothes are very wet, most of the heat in the air stream is utilized to convert the moisture in the clothes into steam and results in only a small rise in the temperature of the clothes. However, as the clothes approach dryness a smaller portion of the heat is used to evaporate moisture and the remainder of the heat in the air stream causes a rapid rise in the temperature of the clothes. If allowed to progress without any interruption this operation would result in the temperature of the clothes being raised to such a point that it would create a fire hazard or the material of the clothes would be damaged. For this reason it is necessary that the heat content of the air stream be reduced as the clothes approach dryness, so that the temperature of the clothes will be maintained at a safe level. By my invention I vary the energy content of the gas supplied to the gas burner of the clothes drying machine to maintain the heat content of the air stream at an optimum level.

It is, therefore, an object of my invention to provide a control system for varying the energy content of gas supplied to a gas burner.

It is a more specific object of my invention to provide an improved control system for maintaining the temperature of the clothes being dried in a clothes drying machine at an optimum level.

It is another object of my invention to provide a temperature-sensitive control for automatically maintaining the temperature of the clothes being dried at a safe level.

It is a further object of my invention to provide such an improved control system in a gas dryer whereby the energy content of the gas supplied to the gas burner is reduced as the clothes being treated approach dryness.

In carrying out my invention, in one form thereof, I provide a clothes drying machine, which, in the usual manner, has a clothes container with suitable means including an electric motor for effective tumbling of the clothes in the container. The clothes in the container are dried by the operation of a gas burner which provides a supply of hot air that is forced through the clothes container by means of a blower. For controlling the temperature of the air forced through the container 1 provide a control circuit including a first thermostat positioned downstream of the clothes container and responsive to the temperature of the air emitted from the container. This first thermostat is connected to the gas burner so that, when the temperature of the air emitted from the clothes container reaches a predetermined level, the electric heater is energized to heat the gas flowing through the pipe. This heating of the gas causes the gas to expand, which results in each unit volume of gas supplied to the gas burner having less energy. Therefore, the heat provided by the burner is reduced and the heat to which the clothes are subjected is also reduced.

I provide a second thermostat which is also located downstream of the clothes container and is responsive to the temperature of the air emitted from the clothes container. The second thermostat is connected to the soleeluding portion of the specification.

noid controlling the valve for the gas burner and, upon the occurrence of a second, higher predetermined temperature, operates the solenoid to completely shut-off the gas supply to the burner, thereby extinguishing the flame. The second thermostat is provided since, with very small loads, even the reduced heat provided as a result of the operation of the first thermostat may cause the clothes to be overheated and it therefore may be necessary to completely eliminate heat for a short period of time.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the con- My invention, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

In the drawings:

FIGURE 1 is a side elevational view of a clothes dryer incorporating my improved dryer control arrangement, the view being partly broken away and partly in section to illustrate details;

FIGURE 2 is a view of the clothes dryer taken along the line 2-2 of FIGURE 1; and

FIGURE 3 is a schematic illustration of my improved control circuit. I

Referring now to FIGURE 1, the machine illustrated is a domestic clothes dryer generally indicated by the numeral 1. Dryer 1 is provided in the usual way with a cabinet 2 having a front door 3 to provide access to the interior of the cabinet for loading and unloading clothes. Provided on the top wall 4 of the cabinet 2 is a control panel 5 which may, in the conventional way, include a suitable manual control 6 connected to a control assembly 7 mounted in panel 5. By manual presetting of control 6, the machine may be caused to start, and automatically proceed through a cycle of operation.

Within cabinet 2, there is provided a clothes tumbling container, or drum 8 mounted for rotation on a substantially horizontal axis. Drum 8 is substantially cylindrical in shape, having a first cylindrical wall portion 9, and second and third outer cylindrical wall portions 10 and 11 located respectively adjacent an annular front wall 12, and a circular rear wall 13 of the drum. Wall portions 9, 1t) and 11 are imperforate over their entire area so that the outer shell of the basket is imperforate. On the interior surface of cylindrical wall portion 9 there may be provided a plurality of clothes tumbling ribs 14 so that clothes are lifted up when the drum rotates, and then tumble back down to the bottom of the drum.

The front of drum 8 may be rotatably supported within outer casing 2 by suitable idler wheels, one of which is shown by the numeral 15. These wheels are rotatably secured to the top of a member I6 which extends up from base 17 of the machine. The wheels 15'are disposed beneath the drum in contact with portion 10 thereof so as to support portion 10 on each side to provide a stable support. 7

The rear end of drum 8 receives its support by means of a stub shaft 18 extending from the center of wall 13. Shaft 18 is secured within a bearing 19 formed in a bafile-like member '20 which in turn is rigidly secured to the back wall 21 of cabinet 2 by any suitable means such as, for instance, welding at a number of points 22. With the arrangement, shown the basket may rotate on a horizontal axis, with rollers 15 providing the front support and stub shaft 18 Within bearing 19 providing the rear support.

In order to provide for the flow of a stream of drying air through the clothes drum, the drum is provided with a central aperture 23 defined by the front wall 12 and a plurality of perforations 24 in its rear wall 13. The

3 perforations in the present case are formed to extend around the rear wall in an annulus.

Referring now to FIGURES l and 2, the dryer 1 is of the type which provides heated air to the interior of drum 8 through perforations 24. The air is heated by a gas flame which issues from the outlet of a convention-a1 inshot burner 26. Burner 26 receives a regulated supply of gas from a solenoid-operated controlling valve assembly 27 of the type conventionally used in gas operated clothes dryers, the gas being supplied to the assembly 27 through a pipe or conduit 28 connected to an appropriate source (not shown) of gas. In the conventional way, primary air is drawn into the burner at the inlet end 29 thereof, and combustion occurs as a result of the mixing of this primary air with gas and its ignition by an appropriate pilot flame (not shown). The gas flame is then spread out, by a suitable member 30 positioned just beyond the outlet end of the burner, within a combustion chamber 31, so that secondary air drawn in through end '32 of chamber 31 is heated to a high temperature.

The outlet end 33 of chamber 31 communicates with an upwardly extending duct 34 which is provided with additional air openings 35, as needed, in order to reduce the temperature of the air and gas mixture to an apporpriate extent. The heated mixture (hereinafter called heated air) then flows up through duct 34, and enters a generaly circular heat diffuser chamber 36 formed between member 20 and a bafile 37 which is rigidly secured to the outer surface of wall 13. Baflle 37 has openings 38 formed therein so that the heated air may flow from chamber 36 through openings 38 and perforations 24 into the drum 8.

It will readily be observed that the combustion chamber 31, duct 34, chamber 36, openings 38 and perforations 24 form an inlet conduit means for the heated air.

The front opening 23 of the drum is substantially closed by means of a stationary bulkhead generally indicated by the numeral 39. Bulkhead 39 is made up of a number of adjacent members including the inner surface 40 of access door 3, a stationary frame 41 formed as a flange of front wall 42 of the cabinet, the inner surface member 43 of an exhaust duct which is formed by the co operation of member 43 with the front wall 42 of the cabinet, and an annular flange 44 mounted on the frame 41 on the duct wall. It will be noted that a suitable clearance is provided between the inner edge of the central aperture 23 and the edge of bulkhead 39 so that there is no rubbing between the drum and the bulkhead during rotation of the drum. In order to prevent any substantial air leakage through aperture 23 between the interior and exterior of the drum, a suitable ring seal 45, preferably formed of felt-like material, is secured to flange 44 in sealing relationship with the exterior surface of drum wall 12.

Central aperture 23, in addition to serving as part of the air flow path through the drum, also serves as a means whereby clothes may be loaded into and unloaded from the drum. Door 3, those inner surface forms part of the bulkhead closing the opening, is mounted on cabinet 2 so that when the door is opened clothes may be inserted into or removed from the drum through the door frame 41. It will be noted that the door includes an outer. flat, imperforate section 46 and an inwardly extending hollow section 47 mounted on the flat outer section. Hollow section 47 extends into the door frame 41 when the door is closed, and the door surface 40 which comprises part of the combination bulkhead 39 is actually the inner wall of the hollow section.

The air outlet from the drum is provided by a perforated opening 48 formed in the inner wall 40 of hollow door section 47. The bottom wall section of door 3 and the adjacent wall of door frame 41 are provided with aligned openings 49 and 50, opening 50 providing the entrance to a duct 51 formed by the cooperation of member 43 with front wall 42. As shown, a lint trap 52, which may comprise a fine mesh bag, is preferably 4 positioned in the exhaust duct 51 at opening 50, the bag being supported by the door frame 41.

Duct 51 leads downwardly to an opening 53 formed in the member 16 which supports wheels 15. Opening 53 constitutes the inlet to a blower 54 contained within a housing 55 and directly driven by an electric motor 56. The blower draws heated air in through perforations 24 in rear wall 13, through the drum, then through the door 3 and duct 51, and finally into the blower. From the blower the air is exhausted from the cabinet 2 through an appropriate duct 57.

In addition to driving blower member 54, motor 56 constitutes the means for effecting rotation of drum 8. In order to effect this, motor 56 is provided with a shaft 58 having a small pulley 59 formed at one end thereof. A belt 60 extends around pulley 59 and also entirely around the cylindrical wall section 9 of drum 8. The relative circumferences of pulley 59 and wall section 9 cause the drum to be driven by the motor at a speed suitable to effect tumbling of the clothes therein. In order to effect proper tensioning of belt 60, there may be provided a suitable idler assembly 61 secured to the same support 62 which supports one end of the motor. Thus, the air is pulled through the drum and at the same time the fabrics in the drum are tumbled. The air is heated by the flame emitted from inshot burner 26, the heated air passing through the drum causes vaporization of moisture from the clothes. The vapor is carried off with the air as it passes out of the machine.

The operation of dryer 1 is controlled by the new and improved control system shown in the circuit diagram of FIGURE 3. As shown therein, the entire control system of the machine may be energized across a 2-wire power supply which includes supply conductors 63 and 64. For domestic use, conductors 63 and 64 will normally be connected across a volt power supply. Motor 56, connected between conductors 63 and 64, is a single-phase induction-type motor having a main winding 65 and a start winding 66, both connected at a common end to a conductor 67. Through a conventional door switch 68 (which is closed when door 3 is closed and is opened when the door is opened) conductor 67 is connected to conductor 64.

The start winding 66 is connected in parallel with main winding 65 under the control of a speed-responsive device, such as that shown at 69, which is schematically shown as connected to rotor 70 of the motor. The speed-responsive device 69 controls a switch 71 which is engagable with either contact 72 or contact 73, being engaged with contact 72 when the machine is at rest and moving into engagement with contact 73 as the motor comes up to speed. It can readily be seen that engagement with contact 72 connects the start winding 66 in parallel with main winding 65, while movement of switch 71 away from this position opens the start winding. Thus, as rotor 70 comes up to speed, the start winding becomes de-energized and the motor then continues to run on the main winding 65 alone.

The starting of the motor is provided for by a manually operable switch 74 which may, for instance, in the structure of FIGURE 1, be moved to its closed position by pulling out on manual control 6. Switch 74 connects the motor to supply conductor 63 through contacts 75 and 76 of a switch 77, which also includes a third contact 78. Switch 74 is normally biased to the open position, as shown; however, when manual control 6 is pulled out, and provided switch 77 is closed, energization of the motor is provided. Within less than a second, under normal circumstances, the motor comes up to speed so that switch 71 engages contact 73. As a result of this movement of the centrifugally operated switch 71, the main winding 65 or motor 56 continues to be energized by the by-pass around switch 74 when manual control 6 is released and switch 74 opens.

A timer motor 79 controls a cam 81 which in turn controls switch 77. Cam 81 is also movable by rotation of manual control 6, so that when operation of the machine is desired, manual control 6 may be rotated until cam 81 causes switch 77 to close all three of its contacts. The machine operation is terminated when cam 81 has been rotated sufliciently by the timer motor 79 to open the contacts of switch 77.

Control of the heat provided by inshot burner 26 is accomplished by the following circuit. Starting at conductor 63, the circuit proceeds through contacts 76 and 78 of switch 77 and then through a conductor 82, a thermostat 83, a conductor 84, a thermostat 85, a conductor 86, the solenoid 87 of control valve assembly 27, a conductor 88, and .a speedresponsive switch 89, conductor 67, and door switch 68 to supply conductor 64.

Thus when contacts 76 and 78 of switch 77 are closed by manual control 6, and assuming that thermostats 83 and 8S and speed-responsive switch 89 are closed, solenoid 87 will be energized to open control valve assembly 27 to supply gas to burner 26.

A parallel branch circuit is provided starting at conductor 82 and proceeding through conductor 90, thermostat 91, conductor 92, heater 93 and conductor 94 to conductor 88.

As seen in FIGURE 2, heater 93 is in the form of a wound heating unit which is mounted upon gas supply pipe or conduit 28 and separated from the conduit by a thin insulator 95. Thermostats 83 and 91 are mounted in housing 55 so as to be responsive to the temperature of the air being exhausted from the drum 8. Thermostat 91 is set to operate at a lower temperature than thermostat 83, for instance, thermostat 91 may be set to operate at 130 F. while thermostat 83 may be set to operate at 140 F. Thermostat 85 is mounted in combustion chamber 31 as to be sensitive to any deviation of the gas flame from its proper path, and thus serves as a safety thermostat.

When wet clothes are placed in the drum 8-and the drying process has begun there is initially only a relatively small rise in temperature of the air exhausted from the drum because most of the heat in the air supplied to the drum is used to vaporize the water in the clothes to form steam. However, as the clothes approach dryness, less and less of the heat supplied is used to vaporize Water and the temperature of the air within the drum rises rapidly. If this rapid rise of the temperature of the air within the drum is allowed to continue the clothes may be damaged. I use thermostats 83 and 91, and their associated circuitry to control the temperature of the air within the drum and thereby assure that the clothes are dried at a safe temperature. Since the thermostats 83 and 91 are positioned in the housing 55 they are effectively responsive to the temperature of the air in the drum and as the temperature of the air increases they operate. The thermostat 91 is responsive to a lower temperature (for instance 130 F.) and closes when this predetermined temperature is reached within the drum to energize heater 93. The heat from heater 93 expands the gas passing through conduit 28 so that the heat content per unit volume of the gas supplied to burner 26 is reduced and, therefore, the temperature of the hot air drawn into the drum 8 is reduced.

With very small loads of clothes this reduced temperature of the hot air supplied to the drum may not be sulficient to keep the temperature within the drum at a safe level; therefore, I set thermostat 83 to operate at a second predetermined temperature (for instance 140 F.) so that, if the temperature continues to rise after thermostat 91 has operated, thermostat 83 will open and de-energize solenoid 87 so that the gas supplied to burner 26 is completely shut-off.

As the temperature in the drum 8 falls, first thermostat 83 closes so that gas will again be supplied to burner 26 and heated air will be provided to the drum 8 and then thermostat 91 opens so that the energy content per unit volume of the gas supplied will increase to increase the temperature of the air provided to the drum. The sequential operation of thermostats 91 and 83 continues until timer motor 79 has rotated cam 81 far enough to separate the contacts of switch 77 and completely shutoff the machine.

Thermostat 85 is provided to insure that the solenoid 87 is de-energized if the flame from the burner 26 deviates from its proper path so that no damage will result from such a deviation.

If the drum stops rotating and the supply of heat is continued the clothes within the drum will not be moved and those in contact with the walls of the drum may be damaged. In order to prevent this I provide speed respons-ive switch 89 which is connected to motor rotor 70 (as schematically shown in FIGURE 3) so that switch 89 will open if motor 56 stops operation to de-energize solenoid 87 and stop the supply of gas to burner 26.

Thus, while in accordance with the Patent Statutes I have discussed what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may he made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all such variations as fall within the true spirit and scope of my invention.

What I claim as new and desire to be secured by Letters Patent of the United States is:

1. A gas burner for producing heat; heating means adapted to heat the gas supplied to said burner for varying the energy content per unit volume of gas sup-plied to said burner; and means for controlling said heating means so as to provide a predetermined energy content in the gas supplied to said burner.

2. In a clothes drying machine:

(a) a container for clothe to be dried,

(b) mean for effecting tumbling of clothes in said container,

(c) a gas burner positioned to supply heat to clothes in said container,

(d) a heater adapted to heat the gas supplied to said burner for varying the energy content per unit volume of gas supplied to said burner,

(e) control means for controlling said heater so as to provide a predetermined energy content in the gas supplied to said burner, whereby the heat to which the clothes in said container are subjected is predetermined.

3. In a clothes drying machine:

(a) a container for clothe to be dried,

(b) means for efiFecting tumbling of clothes in said container,

(c) a gas burner positioned to supply heat to clothes in said container, 7

(d) a heater adapted to heat the gas supplied to said burner for varying the energy content per unit volume of gas supplied to said burner,

(e) a thermostat responsive to the temperature of clothes in said container and efiective to energize said heater in response to a predetermined high temperature of the clothes for reducing the energy content per unit volume of gas supplied to said burner, whereby the heat to which the clothes are subjected is reduced.

4. In a clothes drying machine:

(a) a container for clothes to he dried,

(b) means for elfecting tumbling of clothes in said container,

(c) a gas burner positioned to supply heat to clothes in said container and a conduit for supplying gas to said burner,

(d) an electric heating coil in heat exchange relation with said conduit for varying the energy content per unit volume of gas supplied to said burner,

(e) a thermostat responsive to the temperature of clothes in said container and efiective to energize said heating coil in response to a predetermined high Y temperature of the clothes to heat the gas supplied to said burner for reducing the energy content per unit volume of gas, whereby the heat to which the clothes are subjected is reduced.

5. In a clothes drying machine:

(a) a container for clothes to be dried,

(b) means for effecting tumbling of clothes in said container,

(c) a gas burner positioned to supply heat to clothes in said container and a conduit for supplying gas to said burner,

(d) an electric heating coil wound around said conduit for varying the energy content per unit volume of gas supplied to said burner,

(e) a thermostat responsive to the temperature of clothes in said container and efiective to energize said heating coil in response to a predetermined high temperature of the clothes to heat the gas supplied to said burner for reducing the energy content per unit volume of gas, whereby the heat to which the clothes are subjected is reduced.

6. In a clothes drying machine:

(a) container for clothes to be dried,

(b) means for effecting tumbling of clothes in said container,

() a gas burner positioned to supply heat to clothes in said container,

(d) a valve for controlling the flow of gas to said burner,

(e) a heater adapted to heat the gas supplied to said burner for varying the energy content per unit volume of gas supplied to said burner,

(f) a first thermostat responsive to the temperature of clothes in said container and efiective to energize said heater in response to a first predetermined high temperature of the clothes to heat the gas supplied to the burner for reducing the energy content per unit volume of gas whereby the heat to which the clothes are subjected is reduced, and

8 (g) a second thermostat responsive to the temperature of clothes in said container and effective to operate said valve in response to a second predetermined high temperature of the clothes to cut off the supply of gas to said burner whereby heating of the clothes is stopped.

' 7. In a clothes drying machine:

(a) a container for clothes to be dried,

(b) means for efiecting tumbling of clothes in said container,

(c) a gas burner positioned to supply to clothes in said container and a conduit for supplying gas to said burner,

(d) a valve for controlling the flow of gas to said burner,

(e) an electric heating coil mounted around said conduit for varying the energy content per unit volume of gas supplied to said burner,

(f) a first thermostat responsive to the temperature of clothes in said container and eflFective to energize said heating coil in response to a first predetermined high temperature of the clothes to heat the gas supplied to the burner for reducing the energy content per unit volume of gas whereby the heat to which the clothes are subjected is reduced, and

(g) a second thermostat responsive to the temperature of clothes in said container, said valve having an electrically operated solenoid means, said second thermostat being adapted to actuate said solenoid means when said second temperature is reached to close said valve.

FOREIGN PATENTS 787,912 10/ 1935 France.

0 4 FREDERICK L. MATTESON, 111., Primary Examiner.

JOHN J. CAMBY, Examiner. 

2. IN A CLOTHES DRYING MACHINE: (A) A CONTAINER FOR CLOTHES TO BE DRIED, (B) MEANS FOR EFFECTING TUMBLING OF CLOTHES IN SAID CONTAINER, (C) A GAS BURNER POSITIONED TO SUPPLY HEAT TO CLOTHES IN SAID CONTAINER, (D) A HEATER ADAPTED TO HEAT THE GAS SUPPLIED TO SAID BURNER FOR VARYING THE ENERGY CONTENT PER UNIT VOLUME OF GAS SUPPLIED TO SAID BURNER, 